Girls are having sex at a younger age than a decade ago, according to research.

Almost 38% of 15-year-old girls surveyed by researchers at Edinburgh University had had sexual intercourse.

The figure compares with 26.5% who said they had had sex in a similar questionnaire in 1990.

Dr Candace Currie, from the University's Research Unit into Health and Behavioural Change, said there could be a number of reasons for the children becoming involved in a range of adult activities earlier, including children having greater disposable incomes.

She pointed to research that indicates the number of children smoking has also doubled in the past decade. But she added that the trends were international.

Childhood seems to be getting shorter

Dr Candace Currie, University of Glasgow Research Unit into Health and Behavioural Change

She said: "One of the conclusions you see from other countries is that children embark on an adult lifestyle at a much younger age.

"There are a number of factors that are associated with a rise in sexual activity. Children have a larger disposable income and their lifestyles have changed.

"They tend to be drinking and doing more adult things. Smoking has also doubled in the last decade among 12 to 15-year-olds.

"Early sexual activity is part of the package. It's not an individual lifestyle - there tends to be a peer culture.

"The fact they are embarking on adult lifestyles earlier is because childhood seems to be getting shorter, which is more to do with the increase in the consumer lifestyle of today's teenagers."

The research also indicated that girls with low educational aspirations, and who were not involved in sports were those most likely to be having sex earlier.

Angela Underdown, social policy officer at the Children's Society, said that children's self-esteem and knowledge of sexual health had to be increased.

Wth information and discussion, children will feel empowered ... rather than cave in to peer pressure

Angela Underdown, Children's Society

She said: "At the moment we have the situation in schools where personal health and social education classes are not a part of the statutory curriculum, and they are just tacked on to other classes.

"You may have a brilliant maths teacher, who just isn't equipped to teach sex education to a class of 14-year-olds. Teachers are not given training to teach these classes, and they really should be.

"School has got to be the place where children can get this information - and with information and discussion they will feel empowered to make choices for themselves, rather than cave in to peer pressure."

In the report, compiled for the Health Education Board for Scotland, Dr Currie added that there was no link between sex education in schools and the increase in sexual activity.

She said: "If you look at countries like the Netherlands where there is sex education at a younger age, there is a rise in the age of first sexual encounter."